An ongoing challenge for semiconductor suppliers is to reduce the time used to manufacture integrated circuit (IC) prototypes in a very competitive semiconductor industry. Prototypes are commonly used to develop new technologies. The prototypes can represent the first manufactured silicon for a given design. Prototype wafers usually have the highest priority of all the wafers going through the semiconductor manufacturing process at any given time. One of the many steps involved in the prototype manufacturing process involves the testing of the IC after fabrication.
Because prototype wafers often contain leading edge IC library components, test engineers should determine whether a prototype IC failure is due to a manufacturing defect or because of design issues with the library components used in the IC design. One of the ways to reduce the amount of time used to deliver a prototype IC to a customer is to minimize or eliminate the amount of time the prototype wafers spend sitting on hold (protohold). A factor in protohold is that tests for verifying the functionality of the prototype IC are not available or need modifications.
Many issues exist in reducing protohold turn around time (TAT). Test engineers lack a method to acquire advanced knowledge of which library cells, such as standard cells, core cells or memories, are being used for the first time in an IC design to closely monitor the new cells for possible silicon failures. Setting up special testing procedures for the new cells should be completed before the prototype die reach the test floor. Control for when to change the status of a cell from never been manufactured (i.e., new) to manufacturing complete (i.e., old) are commonly missing. No easy method exists for finding out a list of current designs that contain new library components.
Currently, the test engineers contact the design engineers or other test engineers, who in turn talk to other designers and test engineers to find out whether previous designs used the library components in question and whether the design was manufactured successfully. The current methods depend on a response time of designers and test engineers. The current solution is sometimes inaccurate since prior designs could have been implemented in the library component but were never manufactured. In addition, the test engineer cannot change the status of the library components to indicate if the components have been manufactured successfully. Knowing which library components used in the prototype ICs that have never been through the manufacturing flow before and being able to set up new testing procedures before the wafers arrive on the test floor are desirable to help reduce the protohold time.